ON INDIAN PABASiriC FLIES. 
713 
the body when at rest. Though hundreds of eggs may sometimes be 
seen glued to the hairs of a single horse, the future host does not seem 
to be troubled by the performance. Hatching follows after a few days. 
Perhaps it is the itching caused by the larvae which makes the horse 
lick the places. On reaching the alimentary canal, the parasites 
travel down and ultimately attach themselves by their mouth-hooks 
to the stomach wall. The place of attachment is marked by a depres- 
sion, and the head of the larva becomes more and more deeply plunged 
into the mucous membrane. During this parasitic stage, which lasts 
ten months to a year and includes two moults and three stages of 
larval growth, the larvse feed on the inflammatory products which 
exude from the minute wound. After the bots are detached from 
a horse’s stomach the pitting remains. 
The body of the CEstrid larva consists of twelve segments, of which 
the first two cannot be differentiated from the cephalic ring. No 
head can be recognised. The antennae are rudimentary membranous 
papillae. The problem of respiration during the parasitic time in the 
host’s stomach presents difficulties which are, however, successfully 
solved. On reaching maturity the larvae let go their hold and pass 
out of the horse’s body with the droppings . The larvae are then 
whitish oval maggots, about 20 millimetres long, with rows of brownish 
spines. They are at first lively, but soon burrow into the 
horse-dung or the earth, and there turn into rigid, dark-brown shiny 
pupae. This stage lasts a month or more. The fly emerges by forcing 
open the lid of the puparium, and the life-cycle begins once more. 
Indian elephants are the hosts of CEstrid larvae which attach 
themselves to the stomach walls and go through stages of development 
similar to those of the horse-bots. The flies belong to the genus 
CobboJdia. The parasites of Asiatic elephants are probably of a diffe- 
rent species from those which attach themselves to African elephants. 
The Indian insect, CobboJdia elephantis Cobb., is known, and is a 
large fly with conspicuous reddish head, black wings and body, marked 
with startling white spots at the base of each wing. Eggs of flies 
have often been observed in the erosions at the roots of elephants’ 
tusks. It may be that this is the usual spot chosen by the CEstrids 
to deposit their eggs. Since elephants do not lick their fore-legs or 
flanks like horses, a spot near the root of the tusk gives the newly 
hatched larvse the best likelihood of making their way into the gut 
of the proboscidean. The mature larvse, which have long been known 
in the stomachs of elephants, are much larger than horse-bots, though 
of the same type. Their mouths are furnished with only a single 
pair of strongly curved hooks which act as formidable organs of attach- 
ment to the stomach membrane. 
The history of our knowledge of this parasite of the elephant is 
interesting. Cobbold collected the first larvse from Indian elephants 
